


Dress To Impress

by RatRacer



Category: Gravity Falls
Genre: Crossdressing, F/M
Language: English
Status: Completed
Published: 2018-06-22
Updated: 2018-06-22
Packaged: 2019-05-26 17:23:46
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 3,686
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15005714
Author URL: https://archiveofourown.org/users/RatRacer/pseuds/RatRacer
Summary: Mabel needs help trying on some of her new creations. Dipper volunteers to help. The situation predictably escalates from there.





	Dress To Impress

**Author's Note:**

> A well-received idea + too much free time = my first fic. Enjoy, sickos.

Mabel circled around her brother, looking for any imperfections on the sweater he was wearing. She had not found any problems while working on it or trying it on herself, but having somebody else wear it usually helped her find things she had previously missed. “Could you move your arms around a bit and check if the sleeves aren’t too tight?”

 

Dipper raised his arms up as far as he could while Mabel wrote something down in a notebook. After stretching for a few moments, his arms dropped back down. “It doesn’t feel like they’re too tight." he told her. “Is there anything else you need to check, or are we done?”

 

Mabel walked around him one more time, before putting her notebook down on her desk. “No, I feel like we’ve tested this one enough. But before you go, there’s another thing I’d like you to try on for me. If you’ve got the time for it?”

 

Dipper shrugged. “Sure, I’ve still got half an hour until my show starts." he said as he took off the sweater.

 

Mabel clapped her hands together, took the sweater from Dipper and went to open her closet. “Don’t worry, this’ll take a few minutes, tops! Now where did I hang that thing…" she mumbled to herself as she searched the closet. “...No, nah, not that one, why haven’t I burned those… Aha, there we go!” She turned back to Dipper, holding out a short white and blue skirt. “Put this on so I can check if it’s the proper length.”

 

With a look of confusion Dipper put up an index finger. “Wait, you said you needed my help with testing some of your sweaters. You could’ve told me I’d have to wear other stuff as well!”

 

“That was the only clothes I had planned to work on at first." Mabel responded. “But while I was finishing the last ones I got some ideas for a couple of skirts as well. Do you really think I’d trick you like that?”

 

“Last week you told me the theater group needed a hand for an hour, and I ended up helping them for the entire afternoon.”

 

Mabel opened her mouth to respond, but fell silent for a second instead. “Touché. Anyway, I’m not gonna make you do it if you don’t want to but I’d really appreciate the help. Think you could do that for me?”

 

“I mean, I only reacted like that because you hadn’t told me in advance." Dipper said. “As long as you don’t take any pictures or make me go outside with it on, I’ll do it.” He took the skirt from Mabel and put it on over his pants. “And as long as I don’t need to take off my pants, I suppose.”

 

“No need to take them off, I can see if the skirt’s too short anyway.” Mabel started inspecting the skirt, as well as picking up the notebook and writing some measurements in it. “Looks alright while you’re standing still, try walking around a bit as well.”

 

Dipper walked around the room a couple of times before stopping in front of a mirror. He stood in place for a couple of seconds and did a spin, checking himself out in the mirror. “Yeah, this looks really… like it would fit you pretty well, right?”

 

Mabel looked at him, and let out a small giggle. “Sounds about right. Though your twirling technique could use a bit of work. If you want to practice a bit before your show starts I can give you some pointers…”

 

“I’m good, thanks!” Dipper quickly took off the skirt and handed it over. He began walking to the door but stopped before grabbing the handle. “Just one more thing. Did you say you had ideas for more than one skirt before?”

 

Mabel nodded. “Got two different ones I’m working on right now. I should be done by Friday, so if you’ve got time after school that day you can help me try them on.”

 

“I suppose I can, if you insist…” Dipper said while opening the door and leaving her room.

 

Mabel loudly gasped. “Insist? I don’t insist anything, I simply offered to let you help if you wanted to. If you don’t want to help I’ll just do it myself!" she almost shouted towards the opened door.

 

“Alright, alright. I’d be happy to help you if you let me." Dipper responded from the hall. “That better?”

 

“Much better!” She turned away from the door and to the closet, looking down on the skirt still in her hand and thinking to herself. “ _ So, you’ve got three days to make two different skirt designs. Shouldn’t be too difficult, just gotta come up with something that fits both of our fashion tastes… _ ”

 

* * *

 

As Mabel had predicted, she had two skirts for Dipper to try on after coming home from school on Friday. They had spent the better part of an hour checking out how they look, with Dipper modeling and Mabel writing down her thoughts and telling him what to do. She had even asked him to change into a couple of blouses to see how they fit the skirts, which he had no issues with. In fact, seeing himself in the mirror had made Dipper more excited than he had expected, to the point that he did not feel like waiting for the next time Mabel needed his help.

 

Luckily, Dipper had been on the internet long enough to know what crossdressing was, and knowing it wasn’t an uncommon interest made him less self conscious. And any guilt he might’ve felt about taking his sister’s clothes disappeared when she had come into his room the next day and taken one of his shirts, citing a “wardrobe malfunction” while preparing to go out with some friends.

 

All this was why Dipper found himself standing outside Mabel’s room a few minutes after she had left, double checking to make sure the coast is clear. Seeing no parents or sister coming back for something forgotten, he went into her room and quickly shut the door behind him. Taking a moment to calm his nerves, he went straight for the closet and opened it. He scanned the selection of clothes before his eyes got caught on a cardboard box on the top shelf, the words “ _ For Dipper _ ” written on the side. He moved the box from the shelf to the floor and found a note on top of it. Opening the note, he started to read it.

 

“Dipper, if you are reading this note it probably means that you were going to borrow some of my clothes(if you weren’t, stop reading now). If you were, I’d just like to let you know that I don’t judge you for being interested in that, or for doing so behind my back. After all, why do you think I took your shirt without asking? Anyway, because I’m such a good sister I decided to help you out a little bit. In the box there’s several outfits I picked out that you would look great in. And in case you’re not satisfied or you want some more, just ask me and I’ll see what I can do for you. Have fun! -Mabel”

 

“P.S. And if you happen to want to go the extra mile, I’ve left something else at the bottom of the box… You can’t see it, but I’m wiggling my eyebrows. -Mabel”

 

As soon as Dipper finished reading the note, his mind began to swirl with several questions. “ _ What did she mean with extra mile? How did she know I was getting into it? Does her thinking I’d look great in these mean something more? And why did I just think about that? _ ” He starts to shake his head. “ _ Questions later, gotta get this stuff to my room first. Don’t want mom or dad seeing this. _ ” Pocketing the note, he grabbed the box but stopped himself when he sees Mabel’s mirror. “ _ Crap, I forgot I don’t have a mirror like that in my room. Guess I gotta make do with a hand mirror, if I don’t want to… _ ” Looking towards the mirror, he sighed and put the box down on the bed. “Guess I’m staying in here, then. Not like it’s any more risky than anything that happened during the summer." Dipper said to himself. “Alright, time to check what Mabel’s got in store for me.”

 

Hesitantly, he leaned forward and took the lid off the box, followed by picking out the clothes one by one. Inside the box he found the three skirts he had tried on, the blouses Mabel thought fit best with the skirts, and a green dress. Underneath the dress was nothing but cardboard, which Dipper realized was not the bottom but a loose sheet placed to hide what’s underneath. “ _ If she felt it needed to be hidden, the something else she mentioned must be pretty special. _ ” he thought as he removed the cardboard. “ _ So let’s see what’s insi… what the heck? _ ” Looking down, he saw some of Mabel’s lipstick, a pair of stockings he hadn’t seen before, and a pair of panties he had seen in her laundry before. “ _ Jeez, I get wanting to help me but isn’t giving me your underwear a bit too far? Unless she’s… No, I’ve gotta stop reading too much into this. Let’s focus on what’s actually important here. Do I start with the dress or a skirt? _ ”

 

* * *

 

“Sorry girls, it’s been great hanging out with you but I need to leave now." Mabel said to the surprised group of friends in front of her.

 

“Seriously? We haven’t even been here for an hour, Mabel!" one of the girls said back. “We don’t have any important homework this weekend, so what’s the problem?”

 

Mabel walked up to the girl and waved for the rest of her friends to come closer. “Can all of you keep a secret?” All the girls nodded in response. “Good. The reason I need leave is because I’m meeting up with a guy.”

 

“Wait, really?” “Who is it?” “You want some backup? Or a can of mace?”

 

“Calm down, please!" she told her friends. “I can’t really tell you anything about him, because his family doesn’t seem like they’d be happy with me dating him, so we gotta keep it on the down-low. You understand?” They all nodded again. “Great. And don’t worry, I’ll talk to you all later.” Having said that, she waved goodbye to the girls and walked away.

 

About ten minutes later, Mabel made it back home. She said hi to her parents and made up a story about not feeling so good and having to come home earlier than expected. After that she walked up to the second floor, making sure to stay quiet. “ _ Gotta make sure Dipper doesn’t notice me coming. _ " she thought. “ _ But how do I reveal myself? Can’t be too loud, or scare him so badly he yells. And what if things didn’t go like I planned? Not very likely, but still possible. _ ” As she finished that sentence in her head, she had just reached her bedroom door. “ _ Whatever, just do it like the last exam. Walk in without saying anything and improvise the rest. If it worked then, it definitely works now! _ ”

 

Psyched up, Mabel opened the door and stepped into her room, immediately hearing a gasp from inside. Turning her head, she saw Dipper wearing nothing but a blouse and skirt. He seemed to be in the middle of recoiling from the door, but relaxed after a second.

 

“Phew, for a moment I thought mom or dad had walked in here. Good thing it wasn’t either of them. And I’m guessing it wasn’t a coincidence you came home really early?" he said.

 

“You make it sound like I’m some kind of scheming mastermind. Which I totally am, so you’re right.” While talking, Mabel turned and shut the door. “So, did I pick the proper outfits or what?”

 

“Would be hard to deny that while wearing one of them. Honestly, I’m mostly just surprised you’re this helpful, at first I just hoped you wouldn’t think me liking this was weird." Dipper admitted with a blush.

 

“What, like I’d think anything you do is weird after what happened back in Gravity Falls? Trust me, unless you manage to give me nightmares twice a week I won’t get bothered by it… That came out more depressing than I meant. Let’s change the subject!” Mabel turned to look at the rest of her clothes lying on her bed. “I’m guessing you’ve tried on all the skirts, and the dress, not sure about the stocking, and what’s that I don’t see?” She turned back to Dipper with a look of feigned surprise. “Looks like I was right to add in a pair of my panties, huh?”

 

Dipper turned his eyes away from Mabel, cheeks even redder. “I wasn’t gonna put them on at first cause I thought that would be too much. But as I was trying on all the other stuff, I got more curious how I’d feel if I put them on as well.”

 

“Well, now you’ve got me interested as well.” she answered with a smile on her face. “So tell me, how did they make you feel?”

 

Dipper stayed silent for a few seconds, until he looked back at Mabel. “Let’s just say that’s a bit TMI. I think you can guess the answer from that.”

 

Mabel looked up into the ceiling, stroking her chin. “I dunno, there’s a lot of answers that you wouldn’t want to tell me.”

 

“Oh come on, you know what i meant!”

 

“Hmm, nope. Honestly can’t tell.”

 

“Are you seriously gonna make me say it?”

 

“...”

 

Dipper put his hand to his face and sighed loudly. “Alright, fine. Putting them on kinda turned me on. You happy now?”

 

Mabel focused back on Dipper. “Mhm, definitely. In fact, I’m happy enough that I’ll make things even between us.” As she spoke, she walked up to him and put her hand on his shoulder, and lowering her voice to a whisper. “That kinda turns me on too.”

 

In an instant Dipper’s face went from embarrassed to utterly lost, while the rest of his body tensed up as if he’d been hit. “You’re joking.” he deadpanned.

 

“Oh yeah? Would someone that’s joking do this?” Before he knew what was happening Mabel reached down and lifted the skirt up, giving her a full view of what was going on underneath. As soon as she saw what he’d been hiding, she began blushing even harder than he’d done. “Heh, you really weren’t kidding about it turning you on.”

 

“Mabel, I don’t think we should be doing this.” Dipper replied in a strained voice.

 

“Why not?” She snapped back up to meet his eyes. “Forget about what other people might think, right now all that matters is us. Instead of asking what we should do, ask yourself what you want us to do.”

 

Dipper closed his eyes and took a few deep breaths before answering. “It’s not other people I’m worried about, it’s us. I don’t want things to get awkward or worse if this doesn’t work out.” He opened his eyes again, an awkward smile forming on his face. “But if you can promise me that we’ll be able to sort things out, well… Then I won’t have anything against continuing.”

 

Mabel took both his hands in her own. “Dipper, I promise our relationship won’t be ruined by any of this.” Seeing him nod in response, she led him over to her bed and sat down on the side of it. “Okay, let’s sit down and get this show on the road! Anything in particular you wanna start off with?”

 

He sat down next to Mabel, putting one arm around her back. “It feels a bit strange to have gone this far with someone I haven’t kissed. Could we do that before starting?”

 

Reaching a hand up to Dipper’s cheek, she turned his head to face her before putting her lips on his. Closing her eyes, she felt him mimic the movement and place his free hand on the side of her face as the two began kissing each other. At first they kept to closed-mouth kisses until Mabel angled her head, coaxing her brother to open his mouth. As her tongue began exploring Dipper’s mouth, she slid her hand down from his cheek and let it trail down his front. Once she felt his skirt she stopped, tilting her head a bit as if to ask for approval.

 

Getting Mabel’s message he leaned back and spread his legs out, inviting her to go further. With a small hum from his sister her hand moved down underneath the skirt, tracing the edge of his panties until he felt her fingers on his penis. The panties were quickly moved aside before her hand wrapped around him, and Dipper let out a moan as his foreskin was pulled down.

 

Spurred on by her brother’s moan, Mabel began stroking his cock, slowly moving up and down. While stroking she opened her eyes again and saw her brothers face, scrunched up from the pleasure with his eyes tightly shut. Getting excited by the sight, she started moving even faster and causing him to moan louder. After a few seconds she broke their kiss, looking into his eyes as they opened. “You like that, huh?”

 

“Mhm...”

 

“You like how your sister jerks you off?”

 

“Mhmmm...”

 

Mabel leans in even closer and whispers into Dipper’s ear. “So say it. Say it out loud, and then tell me how I’m making you feel.”

 

“I- I like how my sister jerks me off!” He removed the hand from Mabel’s cheek and put it around her chest, hugging her as the handjob continued. “It feels better than anytime I’ve done it myself, you’re so amazing… Oh god, I’m so close already!”

 

“Yeah, that’s what I like to hear.” She put her thumb on his tip and smeared around the precum forming on it. “Then cum for me, Dipper. Be a good boy and cum for your sister.”

 

“I’ll be a good boy Mabel, I’ll be good...” He hugged her even tighter and his cock began twitching in her hand. “...oh my god i love you iloveyouiloveyouiloveyouiloveyou...” With a cry Dipper came harder than he ever had before, coating his sister’s hand with his cum.

 

“There we go, let it all out-oh wow that’s a lot.” With her brother finally spent, she released his penis and raised her hand to inspect the mess he had made. “Guess I’ve gotta go clean this up. That is, unless you maybe wanna do it for me...”

 

Without responding, Dipper brought his mouth to the back of her hand and began licking and sucking it, making sure to get all the cum off of it until turning to face Mabel. “There, was that good?”

 

Still looking at her hand with wide eyes, it took her a moment to answer him. “Not just good, that was freaking hot. I was not expecting you to actually do it though…”

 

“Hey, after what you did for me I’m willing to do almost anything.”

 

“Almost anything? Well, lucky for you the only thing I can think of right now you’ll probably enjoy too.” Mabel turned to look him in the eyes. “After all that I really need to get off. Wanna help me out?”

 

“Yeah, of course!” Dipper released her from the hug and stood up. “Is there anything in particular you’d want me to do? Cause if you don’t there’s one thing that I’ve been curious about for a while.”

 

With her brother off the bed Mabel took the opportunity to sprawl out on it. “As long as you make me cum I’m fine with whatever.” Making herself comfortable, she quickly took her pants and underwear off. “Alright, let’s see what you’ve got!”

 

Once she was naked from the waist down Dipper moved to the foot of her bed, getting his first view of his sister’s vagina. Not wanting to waste any time, he grabbed both of her legs and pulled her closer to him. Once close enough he went down on his knees and placed his head between her legs, giving her folds a lick. Hearing Mabel moan in response, he set to work kissing and licking everywhere he could reach.

 

“Okay this was definitely a good idea holy crap.” Her legs wrapped around Dippers head while she both her hands went into his hair, making sure he stayed right where he was. “Can you move your tongue up a little bit and flick it?” Feeling him working on her clit, she let go with her hands and laid down flat on her back. “Just keep going, I’m almost there...”

 

After pausing to take a deep breath Dipper dove back down and kept up the pace as asked, going from licking her clitoris to between her lips and back. He only had to keep working for half a minute until his work paid off, as Mabel tightened her leg hold and gave out a long muffled cry. Eventually her legs released his head and he was able to crawl up on the bed next to her, both feeling more satisfied than ever before.

 

* * *

 

Dipper tossed the blouse on the bed, and went to his previously discarded shirt. “Does this mean we’re dating now, or was this a one time thing?”

 

“I don’t think we can be dating if we’ve never gone on a date.” Mabel took the blouse and began folding it up. “And no, what we did in here does not count. But if you want us to start dating, there’s a movie I’ve been wanting to see that comes out Monday evening.”

 

“Works for me.” Picking up his skirt from the floor, he handed it over to Mabel and followed it up with a kiss on the cheek. “However, I do have one condition.”

 

“And what would that be?” she asked him.

 

“You have to choose my outfit.”


End file.
